Jiwei Network reported that the market demand for wireless charging products is currently being released, but the industry technical specifications are still lacking. Therefore, on February 20, 2021, the Ministry of Industry and Information Technology issued the Draft for Comment on the Interim Provisions on radio management of wireless charging (power transmission) equipment, stipulating that the rated transmission power of wireless charging equipment shall not exceed 50W. It is foreseeable that in the future, wireless charging of smart phones will no longer take charging power as the only measure, and high-efficiency wireless charging and building a wireless charging ecology will be the new development direction of the industry.
SC9621 chip
In this context, Shanghai Nanxin Semiconductor has introduced the high-efficiency / high-integration wireless charging RTX chip SC9621. The chip integrates industry-leading low on-impedance power FETs, which can significantly reduce the temperature rise of the chip during high-power charging, thereby improving the experience and value of wireless charging to end customers. At the same time, the SC9621 chip provides high-precision output current sampling over the full load range, helping customers easily cope with demanding foreign object detection (FOD) testing.
In the wireless charging system, there are three major systems: input power, transmission and reception. It is understood that the reason why SC9621 is called RTX (wireless charging receiving + transmitting chip) is because in addition to being a 50W wireless charging receiver chip, it can also be used as a wireless charging transmitter by adding a power supply at the output. At present, the SC9621 chip supports a maximum of 50W received power and 15W transmit power. In the 50W output wireless charging system, Nanxin Semiconductor usually uses a USB power adapter that supports up to 20V output.
In terms of performance, the outstanding advantages of the SC9621 chip are effective in reducing chip heat generation and improving power conversion efficiency. In the system composition of the chip, the current from the coil passes through a synchronous rectifier bridge consisting of four MOSFETs, and the rectifier voltage is output to Vout through The Vrect capacitor filter and LDO, thus outputting the load. Among them, the LDO between Vrect and Vout can effectively block ask ripple. This is because the output voltage (ranging from 3.5-20V) can be set via a digital interface, and the system automatically adjusts the Vrect voltage to keep the dropout voltage on the LDO extremely low.
In terms of power output, if you use a normal 5W BPP transmitter board, the SC9621 EVM can output a maximum of 5V and 1 ampere current soon after it is put in. In larger power output applications, SMD semiconductors save system losses by increasing the output voltage. If it is equipped with the EPP15W transmitter, the SC9621 chip supports a maximum of 12V 1.25A 15W output; if it is combined with the South Core wireless charging transmitter, it can achieve a maximum of 20V 2.5A 50W power output.
SC9621 chip 5W power output display
SC9621 chip 50W power output display
In addition, in order to achieve higher charging efficiency, the SC9621 chip also supports direct charging and high voltage direct charging technology. In direct charging applications, the charging system no longer uses the traditional charger to control the charging current, but adjusts the output voltage of the SC9621 through the charging management chip to achieve the purpose of regulating the charging current. Based on this, since there is no longer a buck or boost charger influence, the charging efficiency of the direct charging system will be greatly improved.
As for how does the SC9621 chip achieve wireless power for other wireless charging receivers? Specifically, the SC9621 enters TX mode by adding 5V current to the Vout end of the SC9621 chip, writing the TX (Wireless Charging Transmitter Chip) instruction through the GUI. At the same time, another SC9621 is placed on its coil as RX (Wireless Charging Receiver Chip) to provide power for wireless transmission.
At present, with the maturity of technology research and development and industrialization, wireless charging has transformed from niche technology to an important charging solution for high-end smartphones. According to data released by research firm Strategy Analytics, the number of smartphones with wireless charging capabilities will reach 1 billion by the end of 2021. This figure is expected to double to 2.2 billion units by 2026. In this regard, the launch of the SC9621 chip by Nanxin Semiconductor is not only the embodiment of the pulse of the times, but also the implementation of the core development concept of "born for efficiency". At the same time, the chip will also bring high-performance, high-quality and cost-effective wireless charging system solutions to the industry.